This invention concerns a device for purifying contaminated gas by passing it through a layer of cleansing liquid. More precisely, the invention relates to a device for purifying gas containing solid and/or liquid particles such as paint particles in the air drawn from painting enclosures or tunnels, such as those used for painting automobile bodies.
U.S. Pat. No. 4,299,602 teaches a gas-purifying device in which a cleansing liquid such as water passes through the device from top to bottom, mixes with the contaminated gas, entrains the particles suspended therein, and is collected in a receiving tank. After the cleansing liquid and the contaminated gas are fed through an upper orifice, they enter a connecting channel which diverges progressively as it extends downwardly, and which connects the cleansing liquid feed orifice to an approximately vertical flow wall(s), a horizontal transverse wall being positioned beneath the feed orifice at the level of the flow wall. The cleansing liquid flows along the flow wall after falling on the horizontal transverse wall, forming a sheet of droplets after impact against said wall, all of which collect in the liquid layer which flows along the flow wall after the particles in suspension are immobilized in the circulating gas. This device allows the collection of all particles in suspension in the contaminated gas requiring treatment.
Nevertheless, until now no device has been able to provide for the continuous flow of the cleansing liquid through the connecting channel joining the cleansing liquid feed orifice to the flow wall. As a result dry areas form on the surface of the connecting channel, and since the liquid does not flow in these areas, the particles in suspension in the contaminated gas adhere to them, thus gradually clogging the device.
Furthermore, such clogging raises an important, heretofore unresolved problem relating to the manufacture of these devices. A major consideration in a contaminated gas cleaner such as the one described in U.S. Pat. No. 4,299,602 is the loss of head caused by the horizontal transverse wall, also called a shield. As stated above, the purification of the gas is effected by droplets formed when the cleansing liquid falls on the shield, these droplets then rebounding toward the flow wall where they are collected after they have entrapped the particles suspended in the contaminated gas.
Accordingly, the shield cannot be positioned at the level of the connecting channel since, as stated above, this channel contains dry areas in which the particle-laden droplets would be smashed, thus clogging the connecting channel.
The sole possibility for remedying the loss of head in a device of this kind would thus consist in the enlargement of the shield by reducing the space between the shield and the flow wall. The only suitable industrial solution has, therefore, always been to halt assembly to dismantle the old shield and to install a new one. This process is, of course, costly and time-consuming.
Furthermore, as evidenced by measurements taken above the liquid feed orifice, a purification device such as that described above functions too noisily. More specifically, and in addition to the excessive general noise level of such a device, the sound spectrum exhibits a peak in the low-frequency range, at about 300 Hz. While high-pitched sounds can be absorbed fairly readily by insulating materials, the much greater difficulty posed by the absorption of low-pitched sounds is well known.